Mother is shivering, complaining of a fever, recently had surgery for breast cancer

My mother, aged 47, is currently lying on the couch, wrapped in quilts with a body temperature nearing 40 degrees C, while at the same time complaining she feels cold, and is visibly shivering.

Apologies for what is likely to be pretty vague information, I haven't been told much about her condition personally, even when I ask about it.

Recently she had an operation for her breast cancer, and from what she and my grandmother have said, she's been getting worse, with a large red rash (Or at least what looks like one according to my grandmother) around her nipple, and near spontaneous headaches occuring.